The present invention relates to tunnel boring machines and more specifically to a tunnel boring machine capable of boring a curvilinear tunnel with horizontally and vertically curved portions of relatively small radius as well as straight line portions.
Tunnel boring machines have long been used in the mining industry for the purpose of cutting generally straight line tunnels and tunnels with curves of large radius (500 feet) through earthen strata. The rock cuttings created by the machine in the boring process are generally removed from the area in which the machine is working by a conveyor or light rail system within the tunnel and moved rearwardly through the tunnel for subsequent transport to a materials handling area. A problem in the use of tunnel boring machines until the present invention has been that in following right of way boundaries or other mining layout plans, it is often necessary to provide for tunnel alignments with small radius curves. When a prior art type tunnel boring machine is used, it is therefore often necessary to periodically stop the machine boring operation and create an enlarged area at the tunnel end face through blasting, manual rock cutting, etc. so that the machine can be reoriented to produce a sharp deflection in the alignment of the tunnel.
It would be generally desireable to provide a tunnel boring machine having the capability of boring curves of small radius as well as curves of large radius and straight line tunnel portions. The machine should also be capable of cutting a relatively tight curve (50 feet) without the need for excessive manual labor operations or blasting at the tunnel face.